A COG (Chip On Glass) technology for a mounting driver IC on a glass of a liquid crystal panel is gaining popularity in compact liquid crystal display panels to be used for cellular phones or the like. However, a plurality of driver ICs are required in case of applying such COG technology to medium or large size liquid crystal display devices.
As liquid crystal panels become larger, there encounters such problems as increasing loads of driver ICs and heat generated in such driver ICs due to increased power consumption. Generation of heat by the driver ICs leads to poor display quality due to different heat distribution between locations of the liquid crystal panel adjacent to the driver ICs and distant from such driver ICs, thereby causing local changes in performance of the liquid crystal panel and ultimately degradation in display quality.
Moreover, increased heat generated by the driver ICs causes de-rating of the driver ICs and poor reliability of the driver ICs.
Prior art to alleviate such problems due to increased heat generation of the driver ICs in the COG technology are proposed in various publications such as JPA2002-83907 entitled “semiconductor device, substrate, and liquid crystal display and plasma display using such substrate” (a first reference), JPA10-214045 entitled “image display device” (a second reference) and the like.
The first reference discloses a technology of providing a heat dissipation plate on the driver ICs. On the other hand, the second reference discloses a technology of providing a heat conductive sheet between driver ICs for a liquid crystal and a front metal case.
However, even the technologies as disclosed in the first and second references require additional members for enhancing heat dissipation, thereby resulting in cost increase.
Furthermore, in the technology as disclosed in the first reference, it is necessary to add a coating step of a protection film for providing the heat dissipation plate. Such additional step in the manufacturing process results in increased cost of the product.